Estudio regional de la elasticidad aórtica porcina utilizando un modelo en derivadas de orden fraccional

Understanding and modelling the mechanical behaviour of the aorta is a problem being treated since several decades ago. Usually, it is assumed that the viscoelastic properties of the aorta gradually change from the heart towards periphery, going from mainly elastic to more viscous vessels. This behaviour might be associated with the gradual diminution of the elastin/collagen ratio and the increase of smooth muscle presence. Nevertheless, some reports show that the mechanical properties of the aorta do not vary uniformly. In this work we performed uniaxial tensile and relaxation tests of four specimens from different regions of a porcine aorta. A test machine conceived and built in our laboratory was adapted to measure stress and strain in a controlled temperature environment. Two models were fit to the relaxation curves: one based on a traditional spring/dashpot arrangement and another one with a fractional-order-derivative element. The latter was more accurate in terms of the root mean square error (−33%) with respect to the traditional model. Moreover, it has 4 instead of 5 parameters to adapt. In this test, we did not find a gradual change in the aortic stiffness: it increased from the ascending to the distal descending segment, whereas a raise was observed in the proximal descending region.